It has been hitherto known that a lithographic printing plate having excellent ink-receptability can be obtained from a presensitized lithographic printing plate precursor having thereon a light-sensitive layer composed of a light-sensitive composition comprising a high molecular compound and a water insoluble diazo resin as disclosed in British Pat. No. 1,280,885 (corresponding to Japanese Patent Publication No. 1167/72), Japanese Patent Application OPI Nos. 24404/72, 38302/72, 9804/73 and 120903/78 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), U.S. Pat. No. 4,123,276 and British Pat. No. 1,460,978.
However, a presensitized lithographic printing plate precursor produced by coating a light-sensitive composition comprising a high molecular compound and a water insoluble diazo resin onto an aluminum support that has been rendered hydrophilic undergoes deterioration in developability with the passage of time during storage, and the non-image areas may thus be stained with ink upon printing.
In order to eliminate the above-described disadvantage, attempts of incorporating various stabilizers in the light-sensitive composition have been made. For example, known stabilizers for this purpose include phosphorous acid (Japanese Patent Application OPI No. 151023/79), oxalic acid (U.S. Pat. No. 4,172,729), halogen-containing organic phosphoric acid ester compounds (Japanese Patent Application OPI No. 3620/75), heterocyclic diazonium salts (Japanese Patent Application OPI No. 143405/76), and phosphoric acid, sulfuric acid, organic sulfonic acids, polyacrylic acid, polyvinylphosphonic acid and polyvinylsulfonic acid (U.S. Pat. No. 3,679,417, Columns 6-7). Nevertheless, these known additives have not been found to produce a sufficiently desirable improvement in stability during storage.